Biodiesel is the name for a variety of ester-based oxygenated fuels made from vegetable oils, fats, greases, or other sources of triglycerides. Biodiesel is a nontoxic and biodegradable blendstock which may be blended with petroleum diesel provided relevant specifications are met. Biodiesel has been designated as an alternative fuel by the United States Department of Energy and the United States Department of Transportation, and is registered with the United States Environmental Protection Agency as a fuel and fuel additive.
Because biodiesel is made from numerous different feedstocks (e.g. rapeseed oil and palm oil), including mixed feedstocks, a finished fuel manufacturer is often not aware of the exact feedstock composition of a purchased biodiesel. Biodiesel is commonly referred to by its feedstock source (e.g. rapeseed methyl ester, palm oil methyl ester). Since the performance of a biodiesel depends upon the particular feedstock mixture from which it was produced, formulators are therefore often unable to predict how the biodiesel will perform in the finished fuel blend. For example, in the absence of accurate feedstock information, it can prove difficult to anticipate whether any given biodiesel will afford a performance advantage such as an improved cetane number, or will in fact suffer from a performance disadvantage (such as poor low-temperature operability) that might call for the addition of a performance enhancer.
Lack of a reliable biodiesel compositional profile also complicates fuel formulators' efforts to design biodiesel blends that satisfy applicable regulatory standards such as ASTM D975, ASTM D7467 Standard Specification for Diesel Fuel Oil, Biodiesel Blend (B6-B20), and EN590. The performance criteria and characteristics mandated by such standards are linked inextricably with a biodiesel's composition.
Giordani, et al., “Identification of the Biodiesel Source Using an Electronic Nose”, Energy & Fuels 2008, 22, 2743-2747, discloses the use of an e-nose and neural networks to identify a biodiesel feedstock source. Eide, et al. “Chemical Fingerprinting of Biodiesel Using Electrospray Mass Spectrometry and Chemometrics: Characterization, Discrimination, Identification, and Quantification in Petrodiesel, Energy & Fuels 2007, 21, 3702-3708, discloses the use of electrospray mass spectrometry (ESI-MS) to discriminate between biodiesel from different feedstocks and manufacturers, to identify fatty acid methyl esters (FAME) and free fatty acids, and to identify and quantify blend composition. Adam, et al., “Using comprehensive two-dimensional gas chromatography for the analysis of oxygenates in middle ditillates I. Determination of the nature of biodiesel blend in diesel fuel”, J. Chromatogr. A 1186 (2008) 236-244, discloses the use of two-dimensional gas chromatography (GC×GC) to quantify fatty acid esters in middle distillate hydrocarbons and individual identification and quantitation of fatty acid acid ester blends with diesel. Catharino, et al., “Biodiesel Typification and Quality Control by Direct Infusion Electrospray Ionization Mass Spectrometry Fingerprinting”, Energy & Fuels 2007, 21, 3698-3701, discloses the use of ESI-MS for fingerprinting and quality control of biodiesels. Tiyapongpattana, et al., “Characterization of biodiesel and biodiesel blends using comprehensive two-dimensional gas chromatography”, J. Sep. Sci. 2008, 31, 2640-2649, discloses a 2-D gas chromatography flame ionization detection method for biodiesel fuels.
The techniques cited in the above references do not provide readily programmable algorithmic techniques that correlate biodiesel FAME composition and feedstock source, and therefore are not well-suited to control of biodiesel fuel blending.
Processes which seek to optimize fuel composition by analysis of the amount of biodiesel in a biodiesel blend, such as the processes described in U. S. Pat. No. 7,404,411, fail to address the formulation problems mentioned above because they merely quantify the amount of biodiesel and do not provide any pre-blending qualitative analysis of biodiesel feedstock.
Accordingly, the need exists for methods which will accurately and conveniently analyze fatty acid alkyl ester-containing biofuels such as biodiesel, which will enable fuel formulators to optimize the design of fatty acid alkyl ester-containing biofuels, and which will facilitate the identification of a fatty acid alkyl ester-containing biofuel's feedstock.